Update: Almost ten years since I started using this method when it was called Skydrive, and still working great! They're finally catching up with the new Folder Protection that moves Desktop, Documents and Pictures into OneDrive. Better check because many found this to be Enabled by default: Turn On or Off Folder Protection with OneDrive in Windows 10
I also like as a secondary backup the newer Google Drive Backup which lets you choose any of your User folders to back up in real time (15gb free) but can't be sync'd via cloud to other devices like this tutorial method can do.
Technical Level : Basic
Here's how to sync User folders across your devices to the Microsoft Cloud, leaving a hard copy on each device if you want while storing them for safe keeping in MS Servers, where you can also access them on the internet.
Keep your files backed-up and synching together across all of your devices using OneDrive built into Windows 8, 8.1 and 10 or in earlier versions of Windows
OneDrive Desktop App for Windows which offers 5gb free cloud storage for each Windows Live/Hotmail/Outlook ID and sells more for cheap.
It can be as easy as dragging anything you want backed up into OneDrive folder which lives both on your HD and in the Cloud, which is the gauzy name for MS Servers. But with a few more minutes configuration you'll have your User folders stored in the cloud ready to access on the internet and sync'd to any of your devices.
After trying several methods for five years I've settled on physically moving the active User folders to the OneDrive folder with the steps in
How to Change the Location of User Folders in Windows 10
You can also place the OneDrive folder on any other HD, but be aware that if it is moved from C and you use Win7 Backup Imaging it will force the inclusion of the data drive to which Onedrive and/or User folders are moved since
they are System folders. I would also in that case not move Desktop beyond C.
You can do the same on all your PC's and have one master set of files hosted and kept Sync'd this way by OneDrive, even access them from any device anywhere via the internet, share them publicly, by invitation, or link.
In using this method the only risk is if you'd delete a file or folder and have it sync on other devices before you realize you still need it. In this case the file/folder will be in each Recycle Bin. For this reason I'd uncheck Recycle Bin in CCleaner so that it is only emptied manually when you have the chance to review contents.
Alternative method using Libraries in Windows 7
If you prefer not to move the User folders into OneDrive folder, you can also copy each one there, delete the content in the C: User folder, then rightclick each User folder in Onedrive to add it to the related Library - Include a Folder - Windows 7 Forums.
If you use this Library method, keep each empty C: User folder in the Library so you can visually monitor if any files land there and simply drag them over to the Onedrive User folder. You may want to leave some files which exceed the Onedrive size limit in C: user folder so they don't cause an oversize error message.
To restore these we need to use the Restore Default Location button in each User folder Properties box. But there are now problems with Documents and Picture restoring because OneDrive also has those folders and when it merges them
it complicates things.
But what always works to restore the User folder is here: Restore Default Location of Personal Folders in Windows 10 Windows 10 User Accounts Tutorials
Back up each folder contents to desktop first just in case.
If you have any questions or feedback please use the Comments section below which I will monitor.